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reading mp3 id3 tags in java...

I am trying to figure out how to read the id3 tag of an mp3 file with java. I think it is a fixed width thing at the end of the file... so is there a way to open a file and get to the end and work backwards or something?
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AndyBeckwith
Asked:
AndyBeckwith
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1 Solution
 
Droby10Commented:
sure...it's been awhile, i'm going off the top of my head, and i don't have a reference available...so this may be a little off.

import java.io.*;

public static void main ( String args[] ) {
  try {
    File f = new File ( args[0] );
    FileInputStream fis = new FileInputStream ( f );
    int flen = fis.available();
    byte sig[] = new byte [ 3 ];
    byte artist[] = new byte [ 30 ];
    byte title[] = new byte [ 30 ];
    byte album[] = new byte [30];
    byte genre[] = new byte [1];
    byte comments = new byte [30];

    int id3len = sig.length + artist.length + title.length + album.length + genre.length + comment.length;

    fis.skip ( len - id3len );    
    fis.read ( sig );
    fis.read ( artist );
    fis.read ( title );
    fis.read ( album );
    fis.read ( genre );
    fis.read ( comments );
  } catch ( Exception e ) {
    e.printStackTrace();
  }
}


also, this code is for id3 version 1 only...which isn't used as much anymore...

id3 version 2 allowed title-streaming, embeded content...etc, and is much more robust...it's also much more difficult to filter as its embeded within the frames of an mp3 document.

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Droby10Commented:
just realized how ugly the code was...be sure to check verify after all of the reads...and close the inputstream at the end.
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AndyBeckwithAuthor Commented:
do you have any info on the v2 tags?
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Droby10Commented:
no...but here's the definitive resource..

http://www.id3.org/
http://www.id3.org/develop.html
http://www.id3.org/id3v2.4.0-structure.txt

you'll also find links for source documentation at

http://id3lib.sourceforge.net/

-hope this helps.
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Droby10Commented:
and actually here's some java source...

http://www.rabbitfarm.com/site/id3.html

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AndyBeckwithAuthor Commented:
Back to your original code...

This is what I did, and it still wont work...

~~~ code ~~~
import java.io.*;
public class ReadId3 {

  public static void main ( String args[] ) {
    try {
      File f = new File ( args[0] );
      FileInputStream fis = new FileInputStream ( f );
      int flen = fis.available();
      byte [] sig = new byte [ 3 ];
      byte artist[] = new byte [ 30 ];
      byte [] title = new byte [ 30 ];
      byte album[] = new byte [30];
      byte genre[] = new byte [1];
      byte comments[] = new byte [30];

      int id3len = 124;

      fis.skip ( flen - id3len );    
      fis.read ( sig );
      fis.read ( artist );
      fis.read ( title );
      fis.read ( album );
      fis.read ( genre );
      fis.read ( comments );
    } catch ( Exception e ) {
      e.printStackTrace();
    }

    for( int i = 0; i < 30; i++ ){
      System.out.print( "" + title[ i ] );
    }
     
  }
}
~~~ end code ~~~

I still get this error:

~~~ error ~~~
ReadId3.java:31: cannot resolve symbol
symbol  : variable title
location: class ReadId3
        System.out.print( "" + title[ i ] );
                               ^
1 error
~~~ end error ~~~

I cant seem to force it to a string...
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Droby10Commented:
your print statement is outside of the try loop where title is defined...title is out-of-scope...if you predeclare it, it should work.

import java.io.*;
public class ReadId3 {

 public static void main ( String args[] ) {
   byte [] sig = new byte [ 3 ];
   byte artist[] = new byte [ 30 ];
   byte [] title = new byte [ 30 ];
   byte album[] = new byte [30];
   byte genre[] = new byte [1];
   byte comments[] = new byte [30];
   try {
     File f = new File ( args[0] );
     FileInputStream fis = new FileInputStream ( f );
     int flen = fis.available();
     int id3len = 124;

     fis.skip ( flen - id3len );    
     fis.read ( sig );
     fis.read ( artist );
     fis.read ( title );
     fis.read ( album );
     fis.read ( genre );
     fis.read ( comments );
   } catch ( Exception e ) {
     e.printStackTrace();
   }

   for( int i = 0; i < 30; i++ ){
     System.out.print( "" + title[ i ] );
   }
   
 }
}
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sudhakar_koundinyaCommented:


No comment has been added lately, so it's time to clean up this TA.
I will leave a recommendation in the Cleanup topic area that this question is:


--  Points to Droby10


Please leave any comments here within the next seven days.
 
PLEASE DO NOT ACCEPT THIS COMMENT AS AN ANSWER!
 
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